Shiny Performance Improvement - r

Question

I am looking for suggestions in improving performance of my shiny app. This shiny app saves data in CSV format when user selects a particular row by clicking on check box. I don't want it to save data every time when user clicks on check box. Hence I created action button so that user clicks on button only when he is done with the checkbox selection of multiple rows.
library(shiny)
library(DT)
mydata = mtcars
mydata$id = 1:nrow(mydata)
runApp(
list(ui = pageWithSidebar(
headerPanel('Examples of Table'),
sidebarPanel(
textInput("collection_txt",label="RowIndex")
,br(),
actionButton("run", "Write Data"),
br(),
p("Writeback with every user input. CSV file gets saved on your working directory!")),
mainPanel(
DT::dataTableOutput("mytable")
))
, server = function(input, output, session) {
shinyInput <- function(FUN,id,num,...) {
inputs <- character(num)
for (i in seq_len(num)) {
inputs[i] <- as.character(FUN(paste0(id,i),label=NULL,...))
}
inputs
}
rowSelect <- reactive({
rows=names(input)[grepl(pattern = "srows_",names(input))]
paste(unlist(lapply(rows,function(i){
if(input[[i]]==T){
return(substr(i,gregexpr(pattern = "_",i)[[1]]+1,nchar(i)))
}
})))
})
observe({
updateTextInput(session, "collection_txt", value = rowSelect() ,label = "RowIndex:" )
d = data.frame(n = rowSelect(), stringsAsFactors = F)
if (input$run == 0)
return()
isolate({write.csv(mydata[as.numeric(d$n),], file = "Writeback.csv" , row.names=F)})
})
output$mytable = DT::renderDataTable({
DT::datatable(cbind(Flag=shinyInput(checkboxInput,"srows_",nrow(mydata),value=NULL,width=1),
mydata), extensions = 'Buttons', options = list(orderClasses = TRUE,
pageLength = 5, lengthChange = FALSE, dom = 'Bfrtip',
buttons = c('copy', 'csv', 'excel'),
drawCallback= JS(
'function(settings) {
Shiny.bindAll(this.api().table().node());}')
),escape=F)
}
)
}), launch.browser = T
)
I want action button to write data in CSV format only when user clicks on action button. Is there any way to improve the code below.
d = data.frame(n = rowSelect(), stringsAsFactors = F)
if (input$run == 0)
return()
isolate({write.csv(mydata[as.numeric(d$n),], file = "Writeback.csv" , row.names=F)})

Answer 1

Why are you not using observeEvent for the actionButton?
observeEvent(input$run, {
updateTextInput(session, "collection_txt", value = rowSelect() ,label = "RowIndex:" )
d = data.frame(n = rowSelect(), stringsAsFactors = F)
write.csv(mydata[as.numeric(d$n),], file = "Writeback.csv" , row.names=F)
})

Answer 2

I think you're looking for the require function req(input$run) or try if(is.null(input$run)==T){return()}